1. Field of the Invention
The present invention relates to a microreactor, and more particularly, to an apparatus which manufactures materials and products using a reaction of fluids in the field of chemical industry and pharmaceutical industry or more specifically, to a microreactor which leads a plurality of fluids through their respective fluid feed channels to merge in one reaction channel and causes these fluids to react with one another while circulating.
2. Description of the Related Art
In the chemical industry or pharmaceutical industry involved in manufacturing of chemicals and reagents, etc., the development of a new manufacturing process using a microcontainer called a “micromixer” or “microreactor” is underway in recent years. A micromixer or microreactor is provided with a microspace (reaction channel) having an equivalent diameter (circle-equivalent diameter) of approximately several μm to several hundred μm when their cross section is assumed to be a circle, connected to a plurality of micro fluid feed channels and leads a plurality of fluids through their respective fluid feed channels to merge in the microspace to thereby mix the plurality of fluids or cause the fluids to react with one another as well as the mixture. The micromixer and microreactor have basically a common structure, but one which mixes a plurality of fluids may be particularly called a “micromixer,” while one whose mixture of a plurality of fluids is accompanied by a chemical reaction may be called a “microreactor.”Therefore, suppose the microreactor according to the present invention includes the micromixer, too.
Such a microreactor is disclosed, for example, in PCT International Unexamined Patent Publication No. WO00/62913, National Publication of International Patent Application No. 2003-502144 or Japanese Patent Application Publication No. 2002-282682. All these microreactors lead two types of fluids through micro fluid feed channels as extremely thin laminar flows to a microspace, and mix and cause the two types of fluids to react with each other in the microspace.
Then, the difference between a reaction by the above described microreactor and a batch type mixture or reaction using a stirring tank, etc., will be explained. That is, a chemical reaction generally takes place when molecules meet together on an interface between reaction fluids, and therefore when a reaction takes place in a microspace, the area of the interface relatively increases and the reaction efficiency increases significantly. Furthermore, with regard to diffusion of molecules itself, the diffusion time is proportional to the square of the distance. This means that as the scale of the microspace is reduced, a mixture of fluids advances through diffusion of molecules without actively mixing the reaction fluids and a reaction is more likely to occur. Furthermore, the scale of the microspace is so small that the flow in the microspace is dominated by the laminar flow, and the fluids diffuse and react with each other in directions orthogonal to each other while flowing in a laminar flow state.
Compared to a conventional batch system using a large volume tank, etc., as a reaction field, the use of such a microreactor allows high accuracy control over the reaction time and reaction temperature between fluids. Furthermore, in the case of the batch system, a reaction advances on a reaction contact surface at the initial stage of a mixture between fluids whose reaction time is short and primary products generated by the reaction between the fluids further continue to be affected by reactions in the tank, and therefore there is a possibility that nonuniform reaction products may be produced. On the contrary, in the case of the microreactor, fluids hardly reside in a microspace but circulate continuously, and therefore primary products never continue to be affected by reactions in the microspace. Thus, it is also possible to extract pure primary products, which would be difficult in the prior arts.
Furthermore, when a small amount of chemical substances manufactured using experimental manufacturing equipment is manufactured in large quantity on an increased scale using large-scale manufacturing equipment, considerable time and manpower would be conventionally required to obtain reproducibility using batch type large-scale manufacturing equipment as opposed to experimental manufacturing equipment. However, based on a concept of numbering up with parallel manufacturing lines using a microreactor according to the amount of manufacturing, there is a possibility to drastically reduce time and manpower to obtain such reproducibility.
On the other hand, the microreactor handles various reactions including reactions at a low reaction rate and taking several tens of seconds to several minutes or a long time such as several hours to complete a reaction. Moreover, there are also reactions which advance in multiple stages and they also take a long reaction time. When the microreactor handles these reactions which take a long reaction time, it is necessary, from the standpoint of reaction control, to circulate fluids carrying out a reaction in the microreactor until the reaction is completed. Therefore, it is necessary to increase the volume of a reaction channel which constitutes a microspace of the microreactor so that the fluids reside for a long time. There are two types of concept when designing such a long residence time microreactor; one is a concept of securing the volume by increasing the cross-sectional area of the reaction channel and the other is a concept of securing the volume by lengthening the reaction channel. The former has a possibility of sacrificing the feature of the microreactor that the reaction channel should be a microspace, and therefore it is desirable to design the microreactor according to the concept of the latter. As a long residence time microreactor, for example, there is a proposal of forming a spiral reaction channel as disclosed in PCT International Publication No. WO 99/44736 or PCT International Publication No. WO02/089965.
However, with regard to the development of a long residence time microreactor with an extended reaction channel, no microreactor has been developed so far which could manufacture a reaction channel which constitutes a microspace easily and robustly and at the same time shorten its manufacturing period and reduce manufacturing cost. The reason is ascribable to the technology of manufacturing a microreactor; the microreactor requires special precision micro processing technology such as photolithography etching, electric discharge machining technology and stereo lithography method, etc., and takes a long manufacturing period and requires high manufacturing cost. Thus, it involves not only a problem that as the length of the reaction channel increases, the manufacturing period and manufacturing cost increase but also a problem that there is limitation to materials and machining dimensions handled by a special precision micro processing technology. On the other hand, attempting to manufacture a microreactor without using any special precision micro processing technology involves another problem that there is limitation to the width of the opening of a reaction channel that can be manufactured and it is not possible to manufacture a satisfactory microspace.
Furthermore, it is possible to realize a long residence time microreactor with an extended reaction channel by spirally winding a tube having an extremely small inner diameter, but lengthening the tube makes the tube easily bendable and causes the reaction channel to be clogged or makes the width of the opening of the reaction channel changeable, which makes it impossible to manufacture a robust apparatus and produces a problem with the accuracy of the apparatus.